SB 

 818 

 C578 

 ENT 



No. 29, Revised Edition. 



itecl States Department of Agriculture, 



DIVISION OF ENTOMOLOGY, 

 L. O. HOWARD, EntomoloKist. 



THE FKUIT-TREE BARK-BEETLE. 



{Scolytus rufjulostiii Eatz.) 



By F. II. ('IIITTKNI)KX, 



l\iil(iiiiiil<)(/ist 1)1 ('/ndi/i' of Jlrci'diiifi E.i jxriiiicnts. 



GENEKAL ('liARACrHKlSTICS AND METHOD OF WORK. 



Orchard trees are subject to the attack of a small lioi'ing insect, the 

 fruit-tree l^ark-heetle {Sroli/fiis rinjithisKs Katz.), its i)resence being 

 manifested by what are callcMl '" worm-holes," minute round openings 



Fni. l.—Scnli/tiis y»r/(//o.s((,s' ; ff.licctli': /j. saiiK' in piDlik'; c. |pu|i;i; tl. laiva— all iiiaij'iiilifil alKiut 

 10 tiinus (aLitlior's illiislratioii). 



ill the outer liark scai'cely a sixteenth of an inch in diameter, accom- 

 panied l)y wiltinu <if the leaves and shi-ivelinu of the bark. and. in the 

 ("ise of stone-fruit ti'ees, l>y more or less copious exudations of uuni. 

 Tlie first appearing holes are made by the parent beetles in entering 

 the bark to deposit their eggs, but later, if no elTort is made to check 

 tiie insect's work, the liark will be found thickly " [x'ppei-ed " with 

 holes as though by line bii-d shot. These are the exit holes of beetles 

 that have in tlieir larval stage mined and develoi>ed undei' the bark. 

 Holes are also made by the mature insects, i)robably chielly males, in 

 the latter days of a season after midsumiiH'i'. evidently for no other 

 ])Ui'pose than for food. A i)iece of twig, showing exit holes in the bark 

 and the galleries of the insects beneath it, is rei)i()diice(l in ligure 2. 



The insect whicli causes this injuiy is a member of the Scol^-tiiUe, a 

 family of cylindrical bark-and-wood-boi'ing l)eetles. The adult or beetle 

 is shown at figure 1, a. It is about one-tenth of an inch in length and 

 tliree times as long as wide; uniform black in color, except the tii)S of 

 tlie elytra or wing-covers and a portion of the legs, which are dull red. 

 The i)unctuatioii of the thorax and of the elyti'a are also illustrate<l and 

 at h the peculiar form of the short atnlomen is shown. This insect is 

 a European introduction and is sometimes known as the shot-borer, 

 orchard scolvtus, and fruit bark-l)ectlc. 



